[PD] GEM : GLSL Mixer - working 2 channel video mixer example

vade doktorp at mac.com
Mon Dec 24 21:35:32 CET 2007

Yes, very efficient, and also give you LOTS of flexibility . the  
regular GL_BLEND_MODES do not offer that many variations (not many are  
useful for video). Want to make a GPU powered chroma key - shader.  
Want to make feedback but have FSAA on, probably shader :)
etc etc. Want to make 4 way mixer? shader! See where I am going here? :)

On Dec 24, 2007, at 3:29 PM, Hans-Christoph Steiner wrote:

> Nice, works for me.  Is the idea that shaders are a efficient way of  
> mixing video?
> .hc
> On Dec 24, 2007, at 12:04 PM, vade wrote:
>> Hello
>> Here is a 2 channel mixer using overlay blend mode with GLSL. This  
>> works, is decently fast and gives me the expected result.
>> If you want more blend modes, feel free to grab them from http://001.vade.info 
>>  (or elsewhere, most are trivial to figure out)- the glsl shaders  
>> for the mixers use the same subroutine layout in the glsl, so it is  
>> trivial to swap. I did not include them out of sheer laziness.
>> Caveats with PD 0.4.03 Extended nightly from Dec 24th (Mac OS X  
>> 10.5.1, QT 7.3, Intel):
>> - had to edit the GLSL program to fix multitexture coordinate  
>> issue. Only can use the texture dims from the zeroths texture unit.
>> - could not get sampler2DRect working at all - only had a single  
>> texel mapped it seemed.
>> - had weird issue where I would sometimes have to close the gemwin  
>> (0, destroy) and then re create it to see the textures assigned to  
>> texture units.
>> 	this happened most often after closing and re-opening the patch.
>> Please see the included question(s) within the PD patch concerning  
>> using framebuffer to grab the output of the rendered shader and  
>> send it to yet another shader. Ive included an exposure shader in  
>> an attempt to make a chain of GLSL effects. I however could not get  
>> gemframebuffer to output any usable texture after using glslprogram.
>> Thanks, hope this is helpful to those out there
>> FUDDLE DUDDLE !@#!@#!@#()*!@#(*@#
>> :)
>> <GEM_glsl_2_channel_mixer.zip>
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> ----------------------------------------------------------------------------
> Using ReBirth is like trying to play an 808 with a long stick.    - 
> David Zicarelli

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